U.S. patent number 11,353,239 [Application Number 16/553,456] was granted by the patent office on 2022-06-07 for sound reduction grille assembly.
This patent grant is currently assigned to Broan-NuTone LLC. The grantee listed for this patent is Broan-NuTone LLC. Invention is credited to Patrick Bouche, Brent Lillesand, Raymond Panneton, Jean-Bernard Piaud, Rick Sinur.
United States Patent |
11,353,239 |
Bouche , et al. |
June 7, 2022 |
Sound reduction grille assembly
Abstract
A ventilation assembly and methods of forming the same includes
a ventilation grille having reducing acoustic bodies configured to
attenuate sound of the ventilation assembly. Arrangement of the
acoustic bodies can form phononic crystal to attenuate sound and
can be tuned to desired sound bands to reduce sounds.
Inventors: |
Bouche; Patrick (Sherbrooke,
CA), Panneton; Raymond (Sherbrooke, CA),
Lillesand; Brent (Milwaukee, WI), Piaud; Jean-Bernard
(Drummondville, CA), Sinur; Rick (Hartford, WI) |
Applicant: |
Name |
City |
State |
Country |
Type |
Broan-NuTone LLC |
Hartford |
WI |
US |
|
|
Assignee: |
Broan-NuTone LLC (Hartford,
WI)
|
Family
ID: |
74681620 |
Appl.
No.: |
16/553,456 |
Filed: |
August 28, 2019 |
Prior Publication Data
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|
|
Document
Identifier |
Publication Date |
|
US 20210063048 A1 |
Mar 4, 2021 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F24F
13/24 (20130101); F24F 7/007 (20130101); G10K
11/162 (20130101); F24F 13/082 (20130101); F24F
2013/242 (20130101) |
Current International
Class: |
F24F
13/24 (20060101); G10K 11/162 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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105765139 |
|
Nov 2018 |
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CN |
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2510900 |
|
Aug 2014 |
|
GB |
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WO-2005073640 |
|
Aug 2005 |
|
JP |
|
Other References
"Design of radial sonic crystal for sound attenuation from
divergent sound source," Gupta, et al., Elsevier--Wave Motion 55
(2015) (9 pages). cited by applicant .
"Acoustic resonances in two-dimensional radial sonic crystal
shells," Torrent et al., New Journal of Physics, Jul. 27, 2010 (20
pages). cited by applicant .
"Radial Wave Crystals: Radially Periodic Structures from
Anisotropic Metamaterials for Engineering Acoustic or
Electromagnetic Waves," Torrent et al., Physical Review Letters,
Aug. 7, 2009 (5 pages). cited by applicant.
|
Primary Examiner: Phillips; Forrest M
Attorney, Agent or Firm: Barnes & Thornburg LLP
Claims
We claim:
1. A ventilation assembly comprising: a main housing defining an
inlet through which air can be received into the main housing and
defining an outlet; a blower in the main housing and operable to
generate a flow of air; and a grille configured to be located
adjacent to the main housing inlet, the grille having a plurality
of acoustic features to reduce sound generated by the blower,
wherein each of the acoustic features comprises two or more
acoustic bodies spaced apart from each other, wherein the acoustic
bodies of at least one acoustic feature are cylindrical and at
least one of the acoustic bodies of the at least one acoustic
feature defines an outer perimeter that is not a circular
cylinder.
2. The ventilation assembly of claim 1, wherein the plurality of
acoustic features are arranged about a grille outlet aperture
defined in the grille.
3. The ventilation assembly of claim 2, wherein adjacent acoustic
features define air flow pathways in fluid communication with the
grille outlet aperture.
4. The ventilation assembly of claim 2, wherein the acoustic bodies
are radially spaced apart from each other.
5. The ventilation assembly of claim 4, wherein the outer perimeter
of each of the acoustic bodies define smooth aerodynamic shape.
6. The ventilation assembly of claim 4, wherein the outer perimeter
of each of the acoustic bodies defines a radial length, and each of
the acoustic bodies of at least one of the acoustic fixtures have
equal radial length.
7. The ventilation assembly of claim 4, wherein the acoustic bodies
of each acoustic feature comprises an outer acoustic body and an
inner acoustic body.
8. The ventilation assembly of claim 7, wherein the outer acoustic
bodies are arranged annularly about the grille outlet aperture.
9. The ventilation assembly of claim 7, wherein the inner acoustic
bodies are arranged annularly about the grille outlet aperture.
10. The ventilation assembly of claim 7, wherein the inner and
outer acoustic bodies of each acoustic feature are arranged with
corresponding circumferential position about the grille outlet
aperture.
11. The ventilation assembly of claim 2, wherein the grille
comprises a first plate defining the grille outlet aperture, the
plurality of acoustic features extending from the first plate.
12. The ventilation assembly of claim 11, wherein the acoustic
features each include at least two acoustic bodies situated to form
a phononic crystal to attenuate sound.
13. The ventilation assembly of claim 12, wherein the phononic
crystals are collectively configured to attenuate sound within the
frequency bands of the ventilation assembly.
14. The ventilation assembly of claim 12, wherein the phononic
crystals are collectively configured to attenuate sound within
either the frequency bands within the range of 160 to 6,300 Hz or
the frequency bands within the range of 20 Hz to 20 kHz.
15. A ventilation assembly comprising: a main housing defining an
inlet through which air can be received into the main housing and
defining an outlet; a blower situated in the main housing and
operable to generate a flow of air and generating sound in a
frequency range of 500-1,000 Hz; and a grille configured to be
located adjacent to the inlet of the main housing, the grille
comprising a first plate defining a grille outlet aperture; a
second plate spaced from the first plate; a plurality of acoustic
bodies arranged about the grille outlet aperture to reduce the
sound generated by the blower, each acoustic body extending from
one of the first plate and the second plate, wherein the plurality
of acoustic bodies comprises at least a first acoustic body and a
second acoustic body forming an acoustic feature configured to
reduce sound generated by the blower, wherein the acoustic bodies
of at least one acoustic feature are cylindrical and the first
acoustic body is spaced less than one foot from the second acoustic
body, wherein the acoustic bodies of the at least one acoustic
feature are not Helmholz resonators.
16. The ventilation assembly of claim 15, the first acoustic body
defining an outer perimeter that is not a circular cylinder.
17. The ventilation assembly of claim 15, at least one of the
acoustic bodies extends between the first and second plate.
18. The ventilation assembly of claim 15, wherein at least one of
the acoustic bodies extends between the first and second plate and
connects to both the first and second plate.
19. The ventilation assembly of claim 15, wherein adjacent acoustic
bodies define air flow pathways in fluid communication with the
grille outlet aperture.
20. The ventilation assembly of claim 15, wherein the acoustic
bodies comprise two or more acoustic bodies radially spaced apart
from each other.
21. The ventilation assembly of claim 15, wherein the outer
perimeter of each of the acoustic bodies defines a radial length,
and each of the acoustic bodies of at least one of the acoustic
features have equal radial length.
22. The ventilation assembly of claim 15, wherein the acoustic
bodies comprise a plurality of outer acoustic bodies and a
plurality of inner acoustic bodies.
23. The ventilation assembly of claim 22, wherein the outer
acoustic bodies are arranged annularly about the grille outlet
aperture.
24. The ventilation assembly of claim 22, wherein the inner
acoustic bodies are arranged annularly about the grille outlet
aperture.
25. The ventilation assembly of claim 22, wherein the outer
acoustic bodies and the inner acoustic bodies define at least one
phononic crystal to attenuate sound.
26. The ventilation assembly of claim 25, wherein the phononic
crystals are collectively configured to attenuate sound within the
frequency bands of the ventilation assembly.
27. The ventilation assembly of claim 15, wherein at least one of
the plurality of acoustic bodies approximates an ellipse.
28. A ventilation grille configured for a ventilation assembly
having a blower, the ventilation grille comprising: a first plate
defining a grille outlet aperture; and a first acoustic feature and
a second acoustic feature, each of the first and second acoustic
feature extending from the first plate and arranged about the
grille outlet aperture to attenuate sound generated by the blower,
wherein the first acoustic feature comprises two acoustic bodies
spaced apart a first distance and the second acoustic feature
comprises two acoustic bodies spaced apart a second distance that
is different than the first distance.
29. The ventilation grille of claim 28, wherein at least one of the
acoustic bodies of the ventilation grille defines an outer
perimeter that is not a circular cylinder.
30. The ventilation grille of claim 28, wherein the sound
attenuation does not require a Helmholz resonator.
Description
TECHNICAL FIELD
The present disclosure relates to devices, systems, and methods for
sound reducing grilles. More particularly, but not exclusively, the
present disclosure relates to devices, systems, and methods for
grilles for use in ventilation of enclosed rooms.
BACKGROUND
Ventilation is commonly applied to maintain desirable air
conditions within confined spaces. For example, common households
may include ventilation devices and/or systems for rooms having
sinks or bath fixtures that use water to remove excess humidity,
noxious odors or other pollutants from the room. Ventilation can
require moving parts to draw air which can create vibrations and/or
sound, yet, reducing excess vibration and/or sound can require
costly upgrades to component parts. Accordingly, there is a need
for improved ventilation with reduced vibrations and/or sound.
SUMMARY
In accordance with an aspect of the present disclosure, a
ventilation assembly may comprise a main housing defining an inlet
through which air can be received into the main housing and an
outlet through which air can exit the main housing, a blower
situated in the main housing and operable to generate a flow of
air, and a grille comprising phononic crystals configured to be
located adjacent to the main housing inlet.
A ventilation assembly is disclosed comprising a main housing
defining an inlet through which air can be received into the main
housing and defining an outlet; a blower in the main housing and
operable to generate a flow of air; and a grille configured to be
located adjacent to the main housing inlet, the grille having a
means for reducing sound. The means for reducing sound can comprise
a plurality of acoustic fixtures arranged about a grille outlet
aperture defined in the grille. Adjacent acoustic fixtures can
define air flow pathways in fluid communication with the grille
outlet aperture. Each of the acoustic fixtures can comprise two or
more acoustic bodies radially spaced apart from each other. The
outer perimeter of each of the acoustic bodies can define smooth
aerodynamic shape. The outer perimeter of each of the acoustic
bodies can define a radial length, and each of the acoustic bodies
of at least one of the acoustic fixtures can have equal radial
length. The acoustic bodies of each acoustic fixture can comprise
an outer acoustic body and an inner acoustic body. The outer
acoustic bodies can be arranged annularly about the grille outlet
aperture. The inner acoustic bodies can be arranged annularly about
the grille outlet aperture. The inner and outer acoustic bodies of
each acoustic fixture can be arranged with corresponding
circumferential position about the grille outlet aperture. The
grille can comprise a first plate defining the grille outlet
aperture and the plurality of acoustic fixtures can extend from the
first plate. The acoustic fixtures can each include at least two
acoustic bodies situated to form a phononic crystal to attenuate
sound. The phononic crystals can be collectively configured to
attenuate sound within the frequency bands of the ventilation
assembly. The phononic crystals can collectively be configured to
attenuate sound within the frequency bands within the range of 160
to 6,300 Hz 1/3 octave band center. The phononic crystals can
collectively be configured to attenuate sound within one or more
frequency bands within the range of 160 to 6,300 Hz. The phononic
crystals can collectively be configured to attenuate sound within
one or more frequency bands within the range of 20 Hz to 20
kHz.
Another ventilation assembly is disclosed comprising a main housing
defining an inlet through which air can be received into the main
housing and defining an outlet; a blower situated in the main
housing and operable to generate a flow of air; and a grille
configured to be located adjacent to the inlet of the main housing,
the grille comprising a first plate defining a grille outlet
aperture; a second plate spaced from the first plate; a plurality
of acoustic bodies arranged about the grille outlet aperture, each
acoustic body extending from one of the first plate and the second
plate. The acoustic bodies can form at least one acoustic fixture.
At least one of the acoustic bodies can extend between the first
and second plate. At least one of the acoustic bodies can extend
between the first and second plate and connect to both the first
and second plate. Adjacent acoustic bodies can define air flow
pathways in fluid communication with the grille outlet aperture.
The acoustic bodies can comprise two or more acoustic bodies
radially spaced apart from each other. The outer perimeter of each
of the acoustic bodies can define a radial length, and each of the
acoustic bodies of at least one of the acoustic fixtures can have
equal radial length. The acoustic bodies can comprise a plurality
of outer acoustic bodies and a plurality of inner acoustic bodies.
The outer acoustic bodies can be arranged annularly about the
grille outlet aperture. The inner acoustic bodies can be arranged
annularly about the grille outlet aperture. The outer acoustic
bodies and the inner acoustic bodies can define at least one
phononic crystal to attenuate sound. The phononic crystals can
collectively be configured to attenuate sound within the frequency
bands of the ventilation assembly. At least one of the plurality of
acoustic bodies can approximate an ellipse.
A ventilation grille is disclosed comprising a first plate defining
a grille outlet aperture; and a plurality of acoustic fixtures
extending from the first plate and arranged about the grille outlet
aperture, each of acoustic fixtures comprising at least two
acoustic bodies defining at least one phononic crystal to attenuate
sound.
The foregoing and other features of the present disclosure will
become more apparent upon reading of the following non-restrictive
description of examples of implementation thereof, given by way of
illustration only with reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
In the appended drawings, where like reference numerals denote like
elements throughout and in where:
FIG. 1 is a perspective view of a non-restrictive illustrative
embodiment of a ventilation assembly consistent with the present
disclosure showing the ventilation assembly installed within a
bathroom;
FIG. 2 is perspective view of the ventilation assembly of FIG. 1 in
isolation;
FIG. 3 is an exploded perspective view of the ventilation assembly
of FIG. 2;
FIG. 4 is a side elevation view of the grille of the ventilation
assembly of FIG. 2;
FIG. 5 is a top plan view of the grille of the ventilation assembly
of FIG. 4 showing a first plate of the grille comprises an outlet
aperture;
FIG. 6 is cross-sectional view of the grille of the ventilation
assembly of FIG. 5 taken along the line 6F-6;
FIG. 7 is a bottom plan view of the first plate of the grille of
the ventilation assembly of FIG. 5 showing a plurality of acoustic
bodies arranged annularly around the outlet aperture;
FIG. 8 is the perspective view of the bottom of the first plate of
the grille of the ventilation assembly of FIG. 7 showing depth of
the acoustic bodies;
FIG. 9 is a diagrammatic view indicating an arrangement of the
acoustic bodies of FIG. 8; and
FIG. 10 is a graphical representation of the sound attenuation
benefits of the present disclosure.
DETAILED DESCRIPTION
Ventilation assemblies, such as ventilation fan assemblies, are
often used to ventilate rooms (e.g. bathrooms and kitchens) in
residential, commercial, and industrial structures. Bathroom
ventilation fan assemblies are often installed in a cutout or
cavity formed in a support member, such as bathroom ceiling or
wall. Traditional ventilation fan assemblies may include grilles or
other air inlet openings through which the fan can draw air from
the room while obstructing direct view of the fan assembly.
Referring to FIG. 1, an illustrative ventilation assembly 12 is
shown installed within the ceiling of a bathroom. The ventilation
assembly 12 includes a main housing 14 (as indicated in broken line
in FIG. 1) located above the surface 16 of the ceiling and grille
18 for receiving air from the room, the grille 18 shown positioned
in close proximity with the surface 16 of the ceiling and adjacent
to an inlet 28 defined by the main housing 14. As discussed in
additional detail below, the grille 18 include acoustic bodies 40
which can reduce the sound resulting from operation of the
ventilation assembly 12.
Referring now to FIG. 2, the main housing 14 defines an inner
cavity 22 which houses a blower assembly 24. The blower assembly 24
includes a fan 26 operable by a motor to draw air from the adjacent
room through the grille 18, through the inlet 28 (via the optional
adaptor ring 32 discussed below) into the inner cavity 22 of the
main housing 14 and out through an exhaust 30. The main housing 14
is illustratively shown as a square box, but in some embodiments
may have any suitable arrangement including any suitable shape
and/or size.
The grille 18 is illustratively arranged adjacent the inlet 28 of
the main housing 14. The grille 18 is depicted as arranged in fluid
communication with the inner cavity 22 via an optional flexible
adaptor ring 32 to communicate air through from the room through
the grille 18 and into the inner cavity 22 in an aerodynamically
efficient manner. The main housing inlet 28 is depicted as an
entire rectangular side of the main housing 14, but could
alternatively be only an aperture the size and shape of the
flexible adaptor ring 32. The grille 18 illustratively comprises a
top plate 34 and bottom plate 36, and means for reducing sound 20
arranged between the plates 34, 36 to attenuate sound. As discussed
in additional detail herein, as air flows through the grille 18,
the means for reducing sound 20 can attenuate sound created by
operation of the ventilation assembly 12.
Referring to FIG. 3, the means for reducing sound 20 comprises a
number of acoustic features 38 arranged to attenuate sound. Each
acoustic feature 38 comprises a set of acoustic bodies 40, each set
of acoustic bodies 40, which each acoustic feature 38, are
collectively arranged to form a phononic crystal to attenuate
sound, as discussed in additional detail herein. Adjacent acoustic
features 38 are spaced apart from each other to define an air flow
pathway 42 therebetween, which is bounded by the top and bottom
plates 34, 36, where present. Both plates 34, 36 are not, however,
required in all embodiments. Air is received from the room through
the grille 18 at the outer perimeters of the top and bottom plates
34, 36, then travels through the airflow pathways 42 and then out
of the grille 18 through an outlet aperture 44 defined in the top
plate 24 and into the main housing 14. As discussed above, the air
may optionally travel through a flexible adaptor ring 32.
Referring now to FIGS. 4 and 5, the top plate 34 illustratively
defines the outlet aperture 44. The grille 18 defines a collar 46
extending upwardly from the top plate 34 for connection with the
adaptor ring 32 to fluidly communicate the outlet aperture 44 with
the inner cavity 22 of the main housing 14. The collar 46 is
illustratively formed hollow to communicate with the outlet
aperture 44 on a first end 48 and with the adaptor ring 32 on the
opposite, second end 50. The collar 46 and the adaptor ring 32
collectively define a flow passage 52 communicating between the
outlet aperture 44 and the adaptor ring 32.
In FIG. 6, the collar 46 is illustratively formed to define a torus
section 54 extending from the plate 34 at the collar first end 48
and a mating section 56 extending from the torus section 54 to
define the second end 50 for engagement with the adaptor ring 32.
The adaptor ring 32 can be separate from the collar 46 and secured
thereto by any known means (e.g. force fit, adhesive, sonic weld,
etc.) or the adaptor ring 32 can be integral with the collar
46.
The collar 46 defines a manifold transition section between the
grille 18 and the ventilation assembly main housing 14 to provide
smooth aerodynamic transition there between. In particular, the
collar 46 extends from the top plate 34 toward the fan 26 to direct
fluid flow toward the fan 46 and preventing fluid flow from greater
access to the main housing inner cavity 22 which can redirect the
fluid flow and/or create unwanted turbulence in the fluid flow,
thereby lowering the efficiency of the ventilation assembly 12.
Stated differently, the collar 46 directs the fluid flow from the
top plate 34 toward the fan 24 in an aerodynamically efficient
manner. The collar 46 can be configured so that the collar second
end 50 approximately reaches the fan 24 upon installation.
Alternatively, the collar second end can be spaced from the fan 24.
The optional adaptor ring 32 can provide additional length to the
collar 46 to lengthen the control of the fluid flow into the main
housing 14 and toward the fan 24. In some embodiments, the collar
second end 50 and/or the optional adaptor ring 32 can be sized to
approximate the inlet of the fan 24 to deliver the fluid flow from
the top plate 34 to the fan 24.
FIGS. 7 and 8 depict an exemplary arrangement of the acoustic
features 38 illustratively includes a pair of acoustic bodies 40,
including outer acoustic body 40a and inner acoustic body 40b,
although in some embodiments, the acoustic features 38 may include
any suitable number of acoustic bodies 40 in forming phononic
crystals. For example, an acoustic feature 38 may include three,
four or more radially spaced acoustic bodies 40. Thus, the terms
"inner" and "outer" when applied to acoustic bodies 40 are relative
and are not to be interpreted as "innermost" and "outermost" unless
context dictates otherwise. The outer acoustic bodies 40a are
arranged annularly around the outlet aperture 44, and the inner
acoustic bodies 40b are also arranged annularly around the outlet
aperture 44, with the inner and outer acoustic bodies 40b,a aligned
along the same radius. Each outer acoustic body 40a is arranged at
a radial distance da.sub.i (e.g., da.sub.1-n for example of 1
through n acoustic features 38) between its centroid Ca.sub.i and a
center axis 25 of the outlet aperture 44 that is greater than the
radial distance db.sub.i (e.g., db.sub.1-n for example of 1 through
n acoustic features 38) between the centroid Cb.sub.i of the
corresponding inner acoustic body 40b of the same acoustic feature
38 and the center axis 25.
Each acoustic body 40 includes an outer perimeter 58 defining
smooth aerodynamic shape, illustrated as approximating an ellipse,
although in some embodiments, any suitable shape may be applied to
each acoustic body 40. The inner and outer acoustic bodies 40a, 40b
of each acoustic feature 38 are radially spaced apart from each
other to define a gap G.sub.i between their outer perimeters 58.
Each acoustic body 40 is arranged to extend longitudinally along
the radial direction relative to the outlet aperture 44.
In the example embodiment of FIG. 7, the most radially inward
portion 60b.sub.i of each inner acoustic body 40b is coincident
with the collar 46, and namely with in the mating section 56 of the
collar 46. Alternatively, the most radially inward portion
60b.sub.i may be spaced from the collar and the outlet aperture 44.
In other alternative embodiments in which the grille 18 has no
collar 46, the inner acoustic bodies 40b can be located on the top
plate 34 and the most radially inward portion 60b.sub.i can be
coincident with the outlet aperture 44. In the embodiment depicted
in FIG. 8, the most radially inward portion 60b.sub.i of each inner
acoustic body 40b defines a height 62b.sub.i extending for
connection with the inner surface of the collar 46, the height
62b.sub.i being larger than a height 64b.sub.i of the most radially
outer portion of the inner acoustic body 40b due to the inwardly
curved section 54 of collar 46. In alternative embodiments, the
acoustic bodies 40 are of uniform height and are placed on a flat
portion of the plates 34, 36. In the illustrative embodiment, the
acoustic bodies 40 are formed as extruded-2-dimensional shapes
having uniform dimensions of their outer perimeter 58 along their
height, but in some embodiments, each acoustic body 40 may have
curvature along its height.
Referring now to FIG. 9, arrangements of the acoustic bodies 40 of
individual acoustic features 38, and of the collective acoustic
features 38 are discussed in terms of exemplary acoustic features
38.sub.i and 38.sub.j arranged adjacent one another. In
particularly, each acoustic body 40 is configured according to a
corresponding elementary cell 66x.sub.i,j (e.g., 66a.sub.1-n,
66b.sub.1-n). Each elementary cell 66 can assist in defining the
dimensions of the corresponding acoustic body 40, the relative
positions between inner and outer acoustic bodies 40a, 40b of the
same acoustic feature 38, and/or the open space between adjacent
acoustic bodies 40, as discussed herein.
For example, in the annular arrangements of the acoustic bodies 40
of the illustrative embodiments, the centroids Ca, Cb of the
acoustic bodies 40a, 40b are arranged co-linear on their
corresponding center lines 35.sub.i,j. The lateral boundaries, and
thus the width, of the elementary cells 66 are defined by the lines
135A, 135B, which are themselves defined at an angle A0 relative to
their corresponding center lines 35.sub.i,j. The dimensions of the
acoustic bodies 40 can be defined in terms of the parameters of
their elementary cells 66. For example, the width of the acoustic
bodies 40a, 40b of each acoustic feature 38 are defined such that
the outer perimeter 58 of the outer and inner acoustic bodies 40a,
40b are respectively tangential to lines 235A, 235B.sub.i that are
defined at an angle A1 relative to their corresponding center lines
35.sub.i,j. An angular ratio of the acoustic body 40 and its
elementary cell 66 can be defined as A1/A0.
The longitudinal (radial) thickness of each cell 66 is defined as
H0. The longitudinal (radial) thickness of each acoustic body 40 is
indicated as H1. A thickness ratio of the acoustic body 40 and its
elementary cell 66 can be defined as H1/H0.
The thickness H0 of the elementary cells 66a, 66b is illustratively
defined to fix the center of the frequency bandgap for attenuation,
according to the relationship k*H0=.pi., where k is the angular
wavenumber in the surrounding fluid (e.g., air). The center of the
frequency band can be defined accordingly to the relationship
.times. ##EQU00001## where c is the speed of sound in the
surrounding fluid (e.g., air). The width of the frequency band gap
and the sound attenuation level are linked to the filling ratio r
of the acoustic body 40 to its elementary cell 66, according to the
relationship
.times..times. ##EQU00002## where S.sub.c is 2-dimensional area
defined by the perimeter 58 of the acoustic body 40, and S.sub.e is
the 2-dimensional area defined by the elementary cell 66. The
filing ratio r is related to each of the angular ratio A1/A0 and
the thickness ratio H1/H0.
The acoustic bodies 40 can be made of any known material and
provides the best performance with made of materials of high
acoustical impedance. The acoustic bodies 40 may be solid or
hollow. In one example, hollow acoustic bodies 40 may be used as
Helmholtz resonators to dampen some frequencies. A solid acoustic
body 40 could comprise an outer shell filled with any material. In
one example, an acoustic body 40 could comprise a shell filled with
a sound reducing material. One or more of the acoustic bodies 40
may be integrally formed as part of the upper plate 34 or the lower
plate 36 or both 34, 36. Alternatively, one or more of the acoustic
bodies 40 may be formed separate from the upper plate 34 and the
lower plate 36 and affixed to one of the upper plate 34 or the
lower plate 36 or both 34, 36 in any known manner consistent with
this disclosure (e.g. adhesive, sonic welding, etc.). The acoustic
bodies 40 may be manufactured by any known process (e.g. injection
molding).
Based on common conditions for bathroom ventilation applications,
exemplary ranges of values can be determined for defining the
arrangements of the acoustic features 38. For example, exemplary
values can be determined for a frequency band of about 200 to about
4000 Hz defined by a 1/3 octave band center frequency as shown in
FIG. 10. Exemplary values for such given conditions can include
angular ratios within the range of about 0.3 to about 0.5 and/or
thickness ratios within the range of about 0.6 to about 0.8.
Exemplary values for the angle of A0 can include A0 within the
range of about 5 degrees to about 10 degrees from centerline
35.
Returning to FIG. 9, with reference to the acoustic feature
38.sub.j, the inner acoustic bodies 40b are illustratively centered
on their corresponding center line 35 together with the outer
acoustic body 40a. However, in some embodiments, the inner acoustic
bodies 40b may be arranged off-center from their corresponding
center line 35.sub.i,j such that their centroid C is spaced apart
from the corresponding center line 35.sub.i,j. For example, as
shown in FIG. 9, the alternative inner acoustic body 40b'.sub.j is
arranged slightly off-center from the center line 35j, such that
the centroid Cb'.sub.j is arranged on a line 45.sub.j which defines
an angle A2.sub.j from center line 35.sub.j. Exemplary values for
the angle A2 for given conditions can include A2 being no greater
than about 1/10th of A0.
The discussion of arrangements of the acoustic bodies 40 applies
generically to each acoustic body 40 of a given acoustic feature
38, yet the acoustic features 38 may be arranged differently from
other acoustic features 38 according to the concepts discussed
above, for example, according to the particular conditions,
physical parameters (configuration of moving parts of the
ventilation assembly, geometries of the grille, etc.) and/or other
internal and/or external factors. Adjacent acoustic features, such
as acoustic features 38.sub.i,j may differ in their arrangements
but with preferred relationships there between, for example, to
maintain overall circularity for the annular arrangements of the
illustrative embodiments. Exemplary relationships can include
variation of angles A0.sub.i and A0.sub.j of adjacent acoustic
fixtures 38.sub.i,j relative to each other within the range of
about 1/1.2 to about 1.2. Exemplary relationships can include
variation in the thicknesses H0.sub.i and H0.sub.j of adjacent
acoustic fixtures 38.sub.i,j relative to each other within the
range of about 1/1.2 to about 1.2.
Referring to FIG. 10, a comparison is shown of the sound levels of
an example ventilation assembly operating with a Stack Grille with
the sound levels of the example ventilation assembly operating with
the grille 18 according to the present disclosure (indicated as
Meta Grille). Within the target 1/3 octaves (1/3 octave center band
frequencies from 160 Hz to 6300 Hz) the level of sones from the
Meta Grille were significantly reduced compared to the Stack
Grille. A grille according to the description herein, including the
example Meta Grille, with or without structural alterations within
this disclosure, would reduce the level of sones in other frequency
bands as well.
It should be noted that the various components and features
described above can be combined in a variety of ways, so as to
provide other non-illustrated embodiments within the scope of the
disclosure. As such, it is to be understood that the disclosure is
not limited in its application to the details of construction and
parts illustrated in the accompanying drawings and described
hereinabove. The disclosure is capable of other embodiments and of
being practiced in various ways. It is also to be understood that
the phraseology or terminology used herein is for the purpose of
description and not limitation.
Although the present disclosure has been described in the foregoing
description by way of illustrative embodiments thereof, these
embodiments can be modified at will, without departing from the
spirit, scope, and nature of the subject disclosed.
* * * * *